The present invention relates to voltage regulators, and more specifically to a sub-cycle static voltage regulator that is able to adjust for input voltage anomalies in one cycle or less.
It is recognized that commercial power systems are subject to various types of disturbances that adversely affect the operation of sensitive electrical equipment. These disturbances usually show up as xe2x80x9cSagsxe2x80x9d or xe2x80x9cSwellsxe2x80x9d in the system voltage.
Disturbances in electrical utility supply networks (transmission and distribution) might be caused for a variety of reasons. Power equipment faults and insulation failures, line switchings, capacitor switchings, large transformer and motor energizations, and non-linear loads such as arc furnaces, variable speed drives, rectifiers, etc. are only a few such causes. Such transient disturbances, as distinguished from complete power failure, manifest themselves as momentary power supply interruptions, voltage sags, voltage transients, voltage magnitude variations, and harmonics. Thus, voltage sags and swells may be caused by failures or switchings within a particular transmission or distribution line.
Several methods are available for dealing with such sags and swells, but most methods have costs (on a per kW basis) that make them unattractive for large load applications. Examples of conventional power quality improvement technologies are uninterruptable power supplies (UPS) and dynamic voltage regulators (DVR). These types of devices require a DC to AC power converter of some type, however, leading to greater complexity and higher cost. Therefore, there is a recognized need for a high speed voltage regulation systems suitable for medium voltage (15 kV class) applications.
To solve the aforementioned disadvantages of conventional regulators, the present invention relates to a voltage regulator that is able to adjust for input voltage anomalies in one cycle or less. The regulator comprises a transformer having a primary winding and a secondary winding, a plurality of further windings selectively connected to the primary winding or secondary winding, and a plurality of solid state switches respectively coupled to each of the plurality of further windings to either i) connect the further winding in series with the primary winding or the secondary winding or ii) bypass the further winding.
According to one aspect of the present invention, the solid state switches are thyristors.
According to another aspect of the present invention, the switches are gate turn-off (GTO) devices.
According to yet another aspect of the present invention, the regulator transformer includes a tertiary winding.
According to a further aspect of the present invention, the regulator includes a controller to control the solid state switches.
These and other aspects of the invention are set forth below with reference to the drawings and the description of exemplary embodiments of the invention.